Chemical Energetics Flashcards

Vocabulary flashcards for chemical energetics based on lecture notes.

Enthalpy (or heat content)

The total chemical energy inside a substance.

Energy level diagram

A representation of the energies of reactants, transition state(s), and products during a reaction.

Transition state

A stage during a reaction where chemical bonds are partially broken and formed.

Activation energy (Ea)

The minimum energy needed for reactant molecules to have a successful collision and start a reaction.

Standard enthalpy change of reaction

The enthalpy change when reactants in a stoichiometric equation react to give products under standard conditions.

Standard enthalpy change of formation

The enthalpy change when one mole of a compound is formed from its elements under standard conditions.

Standard enthalpy change of combustion

The enthalpy change when one mole of a substance is burnt in excess oxygen under standard conditions.

Standard enthalpy change of neutralization

The enthalpy change when one mole of water is formed by the reaction of an acid with an alkali under standard conditions.

Exothermic reaction

A reaction where the products have less energy than the reactants, releasing heat.

Endothermic reaction

A reaction where the products have more energy than the reactants, absorbing heat.

Standard conditions

A pressure of 101 kPa, a temperature of 298 K (25 oC), and each substance involved in the reaction is in its normal physical state (solid, gas or liquid)

Enthalpy (H)

The total energy associated with the materials that react.

Exact bond energy (Bond Enthalpy)

The amount of energy required to break one mole of a specific covalent bond in the gas phase.

Average bond energy

An average of bond energies for the same type of bond in different molecular environments.

Standard enthalpy change of atomization

The enthalpy change when one mole of gaseous atoms is formed from its element in its standard state under standard conditions

Hess’s Law

The total enthalpy change in a chemical reaction is independent of the route by which the chemical reaction takes place